As examples of wiring boards of this kind, there are ones described in Patent Literature 1 to 4. One of them is shown in FIG. 7, which is an enlarged cross-sectional view of the proximity of an electronic component implemented on the upper surface of the multilayer wiring board.
Referring to FIG. 7, a multilayer wiring board 110 comprises a plurality of wiring sheets 112a, 112b and a plurality of electrical insulating sheets 114a, 114b, 114c, and these sheets 112a, 112b, 114a, 114b, 114c are layered alternately in their thickness directions.
Although only two wiring sheets 112a, 112b and only three electrical insulating sheets 114a, 114b, 114c are shown in the example shown in the figure, the multilayer wiring board 110 may comprise more wiring sheets and more electrical insulating sheets.
Each of the wiring sheets 112a, 112b comprises a sheet-like member made of ceramic, polyimide resin, or the like and a plurality of internal wirings 116 made of a conductive material such as copper at least on the upper surface of the sheet-like member.
Each of the electrical insulating sheets 114a, 114b, 114c is made of an adhesive material such as polyimide resin and is piled up over one of the wiring sheets 112a, 112b to cover the internal wirings 116.
The electrical insulating sheet 114a located at the uppermost layer of the multilayer wiring board 110 has a plurality of electrodes 122 to implement the electronic component 120 on the upper surface of the multilayer wiring board 110 (the electrical insulating sheet 114a). Each electrode 122 shapes an annular or rectangular flat land.
Each internal wiring 116 of the wiring sheets 112a, 112b and each electrode 122 of the uppermost electrical insulating sheet 114a are electrically connected by a conductive portion 124 such as a conductive through hole penetrating the multilayer wiring board 110 in the board thickness direction.
Although only one set consisting of two electrodes 122, two conductive portions 124, and one electronic component 120 is shown in the example shown in the figure, more and multiple sets each consisting of electrodes, conductive portions, and an electronic component are actually provided.
Each electrode 122 has a foot pattern 126 formed on the upper surface of the uppermost electrical insulating sheet 114a in a layer shape made of a conductive material such as copper and a connection land 128 formed on the upper surface of the foot pattern 126 to implement the electronic component 120.
Each electronic component 120 has a component main body 130 and a pair of terminals 132 protruded from both the ends of the component main body 130 and is attached to the adjacent electrodes 122 at both the terminals 132 by jointing materials 134 such as solder, conductive adhesive, or the like.
In the example shown in the figure, the electrical insulating sheet 114c located at the lowermost layer of the multilayer wiring board 110 also has a plurality of electrodes 136 on its lower surface. Each electrode 136 is electrically connected to the conductive portion 124 and is electrically connected to another board arranged on the lower side of the multilayer wiring board 110. Although only two electrodes 136 are shown in the example shown in the figure, more electrodes 136 or as many electrodes 136 as the number of the conductive portions 124 are actually provided.
In the multilayer wiring board 110 of this kind, the foot pattern 126 may be separated from the uppermost electrical insulating sheet 114a due to lack of close contact (especially, adhesiveness) between the foot pattern 126 (or the electrode 122) and the uppermost electrical insulating sheet 114a, impact applied to the multilayer wiring board 110, etc.
When the foot pattern 126 is separated as above, failures occur such as breakage of the connection land 128 formed on the foot pattern 126 or breakage of the electrode 122 itself or separation of it from the electrical insulating sheet 114a due to separation of the connection land 128 together with the foot pattern 126 from the electrical insulating sheet 114a. 
As a result, in the conventional multilayer wiring board 110, the electronic component 120 is electrically separated from the internal wiring 116 or comes off from the multilayer wiring board 110, and the multilayer wiring board 110 and an apparatus equipped with this cannot be used.
When the electrode 122 is broken or separated as above, fixing or repair for electrically connecting the electronic component 120 attached to the broken or separated electrode 122 to the corresponding internal wiring 116 is done.
In the conventional multilayer wiring board 110, since the electrodes 122 are just provided in the uppermost electrical insulating sheet 114a, repair is inevitably done by means of keeping the broken or separated electrode 122, especially the foot pattern 126, on the electrical insulating sheet 114a by covering it with resin or soldering a material such as copper foil to the connection land 128 separated together with the foot pattern 126.
However, the above repair method requires a great deal of labor and skills for the repair work and causes problems of adverse effects on the electrical connection characteristics such as impedance matching between the electronic component 120 and the electrode 122 after repair and on the mechanical strength of the repair part and its proximity.
The aforementioned breakage or separation of the electrode 122 occurs not only in a case where the electrode 122 consists of the foot pattern 126 and the connection land 128 but also in a case where the electrode 122 is formed to be a single layer.    Patent Literature 1: Japanese Patent Appln. Public Disclosure No. 5-218218    Patent Literature 2: Japanese Patent Appln. Public Disclosure No. 6-152141    Patent Literature 3: Japanese Patent No. 2961859    Patent Literature 4: Japanese Patent Appln. Public Disclosure No. 2006-120738